Supernova-powered bow shock creates cosmic spectacle

NOW that's one groovy star. Seen speeding like a bullet through a cloud of dust and gas, the massive star Zeta Ophiuchi is creating a colourful wave known as a bow shock. This happens because the star's motion is compressing dust grains like water at the bow of a ship.

To the naked eye Zeta Ophiuchi is a placid dot parked in the constellation Ophiuchus. But the infrared vision of NASA's Spitzer Space Telescope shows how the shooting star is electrifying its surroundings. It creates a scene akin to a UV-triggered fluorescent blacklight poster, says Spitzer image specialist Robert Hurt of the Jet Propulsion Laboratory in Pasadena, California.

In this picture infrared wavelengths have been translated into visible ones, with shorter waves in blue, middle waves in green and longer ones in red. That's why the bright stars glitter like sapphires, while small dust grains fluoresce in a faint teal as they absorb Zeta Ophiuchi's light. Red in the bow shock comes from the larger, hotter dust grains that can survive the star's fierce radiation.

Given its speed and direction, astronomers think the star once orbited an even heftier companion. But the biggest stars live fast and die young, and its partner exploded in a violent supernova blast that sent Zeta Ophiuchi careening away at a whopping 87,000 kilometres per hour.

This isn't the first or even the fastest runaway but it is perhaps one of the most detailed. "Here you have a star hurtling through space and having a huge impact on its environment," says Hurt. "It really gives you a general sense of how everything is interconnected."

Relative to where it used to be, Roger. Or, maybe, crossing a line between our viewpoint and the background stars. Just a couple of suggestions both of which perhaps define our understanding of the word "speed".